PROJECT SUMMARY This application is for a mentored research and career development program that will enable a motived junior physician-scientist to develop the skills necessary to ultimately become an independent investigator. Successful completion of this project will enable the investigator to gain the sills and knowledge necessary to launch a career investigating the mechanisms responsible for the lung damage present in bronchpulmonary dysplasia (BPD) and potentially develop targeted therapeutics to reverse or cure this damage. BPD is a lung disease that affects more than 14,000 premature infants each year with prolonged health ramifications that affect lung function throughout the patient's life. No curative therapies currently exist for BPD. In previous work, we have shown that epigenetic silencing of a cluster of microRNAs, called miR-17~92, is associated with severe BPD in human patients and murine models of the disease. In order to establish a causal relationship between altered miR-17~92 expression and a BPD phenotype, this project will investigate the central hypothesis that: murine genetic partial-deletion (or haploinsufficiency) of the miR-17~92 cluster will alter alveolar and vascular development reminiscent of a BPD phenotype via exaggerated TGF-?, collagen and matrix metalloproteinase expression. In Aim 1, in vivo and in vitro systems will be used to determine the effects of miR-17~92 haploinsufficiency on pulmonary epithelial development and function. A causal relationship will be determined by reintroduction of miR-17~92 using a viral vector to establish return of function and phenotype. Since there is significant cellular cross-talk driving alveolar and vascular endothelial development, Aim 2 will quantify the effects of haploinsufficiency on pulmonary vascular endothelial development and function. Similar to Aim 1, a causal mechanism will be established with return of function experiments by reintroduction of the full expression of miR-17~92 by viral vector. This novel study will impact the field through understanding the cellular mechanisms altered by suppression and subsequent restoration of the miR-17~92 cluster. Furthermore, this study is significant because it provides a model to investigate the cellular mechanisms responsible for alveolar and vascular endothelial simplification that occurs in traditional BPD models without the confounding free-radical damage caused by high oxygen exposure. The above outlined aims will be investigated in an environment with an established history of successful mentorship of junior faculty to independence. Under the supervision of an expert advisory committee, the applicant will 1) Advance her technical skills, with acquisition of as murine pulmonary function testing, immunohistochemistry, and next generation sequencing techniques; 2) Learn advanced biostatistics; and 3) Learn delivery mechanisms of targeted therapeutics. Future independent studies will likely focus on the developmental interplay between the alveoli and vascular endothelium, and use of the miR-17~92 cluster as a biomarker and/or therapeutic target for BPD.